The present invention relates to a hydraulic system.
A conventional hydraulic system is disclosed in JP-A-2000-333364. This hydraulic system is comprising a hydraulic pump driven by a hydraulic pump motor, a hydraulic actuator driven by pressure oil supplied from the hydraulic pump and power supply means. The power supply means has a battery and a stack of a fuel cell supplied with fuel gas and oxidant gas to generate electric power so that power is supplied to the hydraulic pump motor.
In this hydraulic system, the hydraulic pump motor can be driven by the battery and stack. Therefore, even when power of the battery runs short, the hydraulic pump motor can be driven by the stack, and the hydraulic actuator can be driven by the hydraulic pump. Furthermore, the battery can be prevented from falling into over-discharge, so that decrease in the lifetime of the battery can be prevented, and also this hydraulic system has an excellent effect from the viewpoint of noise and environment.
However, in the conventional hydraulic system, the pressure oil supplied from the hydraulic pump is supplied only to drive the hydraulic actuator, and energy is wastefully consumed.